How can i drop my mesh on floor with rigid body
Ok, I tried a few options and got a fairly stable simulation. Here is the result:

Steps:

Scale the ground and pen up by 100 (physics simulations work better with larger objects. Also, the floating came from the constant collision margin of 4 cm which means that objects will already collide when they are 2*4 centimeters apart. While this value can be changed, it is better to scale the objects up)
Apply the scale on the pen with Ctrl+A &gt; Scale
Set the origin of the pen to Center of Mass (Volume) (a wrong origin can mess up simulations)
Use convex hull as collision shape (should be precise enough in this case. Mesh shape causes glitches)
Use box as collision shape for the ground (except if you want to use a different shape)
Finally, you might want to increase the Rigidbody simulation steps (Go to Scene Properties &gt; Rigid Body World and increase Steps per Second and Solver Iterations, e.g. to 600 and 100)